Such hydrogen evolution cells comprise an anode chamber and a cathode chamber inside a casing which chambers are separated from one another by a separator. Corresponding cells comprising a metal anode in the form of a zinc paste, a hydrogen electrode and an aqueous electrolyte are known from DE 35 32 335 A1 and EP 1 396 899 A2, for example.
In hydrogen evolution cells, the hydrogen reaction gas is stored chemically in the form of water being the main constituent of the electrolyte and generally unpressurized. In the case of cells having a metal anode made of zinc, the evolution of hydrogen occurs according to the following reaction equations:Anode reaction: Zn+2OH−→ZnO+H2O+2e−Cathode reaction: 2H2O+2e−→2OH−+H2 Total reaction: Zn+H2O→ZnO+H2.Thus, in the course of the above reaction, the zinc contained in the cell is oxidized to zinc oxide while hydrogen gas develops at the cathode.
Generally, hydrogen evolution results in a slight overpressure in the cells. If the overpressure increases further, there is a risk that the separator bulges and exerts a pressure on the anode chamber, as a result of which electrolyte can leak from the cell. In other words, hydrogen overpressure can be the cause for the occurrence of leaks.
Moreover, since the casings of hydrogen evolution cells are generally formed in two parts and comprise a cell cup and a cell lid, laborious measures have to be taken to achieve a hermetic sealing of the cells. Usually, that is effected by using sealing rings and crimping or screwing of the cell cup and the cell lid.
Thus, such hydrogen evolution cells have several potential leakage spots or constructional designs which might result in leaks at the expense of the service life of the cells.
Thus, it could be helpful to provide a hydrogen evolution cell which avoids deficiencies described above in the context of hydrogen evolution cells and, which in particular, has a significantly reduced risk regarding the occurrence of leaks as compared to known hydrogen evolutions cells.